This invention relates to an apparatus for forming a floating wave barrier for reducing or eliminating the kinetic energy of water waves.
Waves are generated at sea by virtue of the frictional drag exerted on the water surface by the wind whereby the small waves originally generated gradually build up to larger waves to form a pattern which progress towards the shore. It has been determined that the water particles making up the wave travel in a circular or elliptical orbit and that the diameter of the orbits at the water surface equal the height of the wave. Furthermore, it has been determined that the diameter of the orbit at a depth of about half the wave length is only about 4 percent of the orbital diameter at the water surface. Thus, substantially all of the kinetic energy of the wave is concentrated at or near the water surface and the percentage of wave kinetic energy located at a given water depth rapidly decreases with water depth. Thus, a water barrier located at or near the water surface and which extends toward the sea bottom a depth of about one-half the expected wave length can be highly effective in diminishing the wave kinetic energy.
In operation, the incident wave strikes the wave barrier which diminishes the kinetic energy of the wave by forming a reflected wave having a finite kinetic energy and allowing a transmitted wave to pass therethrough which has little kinetic energy. It is desirable that the reflected wave kinetic energy be maximized so that it impinges on the other incident waves to decrease their kinetic energy prior to striking the wave barrier. The difference between the kinetic energy of the incident wave and the sum of the transmitted and reflected waves constitutes the kinetic energy absorbed by the wave barrier.
It has been proposed in U.S. Pat. No. 3,353,361 to employ a floating wave barrier comprising a plurality of weighted automobile tires attached with a flexible chain depending from a fixed support so that when placed in water the tires are located at different depths. This wave barrier is undesirable since it functions primarily to reduce the horizontal wave velocity component with little effect on the vertical wave velocity component. Since the net horizontal component is constantly directed landward, there is a constant substantial force on the fixed supports. In contrast, it would be desirable to provide a wave barrier which acts to reduce the vertical wave velocity component since the net vertical component is changing direction constantly and acts over a relatively short distance equal to about one-half the wave length so that the force exerted on the wave barrier anchor is reduced.
The invention disclosed in U.S. Pat. No. 3,848,419 discloses a floating wave barrier comprising at least one vessel having a top, walls and an open bottom which, when placed in water, has the open bottom submerged. The vessel has at least one plate member attached to the outside surface of the vessel and extending around all or a major portion of the vessel periphery. The vessel or vessels, when placed in water, contain a gas and water. When a plurality of vessels are employed, they are connected with at least one flexible line and one vessel is connected to an anchor on the sea bottom so that when the barrier is placed in water, the vessels are positioned at different vertical levels, with the top member being at or near the surface of the water. The remaining vessels or, if only one vessel is employed, plate members are submerged but near the water surface so that they are located within the top portion of the wave where the major portion of the wave energy is encountered. When placed in water, the vessels and plate members are fixed to prevent substantial movement in the horizontal direction but are free to move in a vertical direction within the wave with the vertical movement of the connected vessels and plate members being out of phase with each other.
The wave barrier disclosed in U.S. Pat. No. 3,848,419 provides excellent wave dampening. However, it would be desirable to improve its performance in reducing kinetic energy of incoming waves.